This invention relates to a television titling apparatus that receives digital input signals corresponding to title information and generates video signals for displaying the information in readable form and, more particularly, to such an apparatus wherein predetermined adjacent characters are presented in overlapping positions on a display.
Systems for converting digital title information into video signals that are suitable for display in readable form are currently in widespread use. These systems are employed, for example, to provide title information alone on a display screen, such as is typically done with financial data. Title information may also be generated for display in conjunction with conventional television picture information. This is generally accomplished by combining the video picture signal and the video title signal using known keying techniques.
A system that receives digitally coded characters and generates character video signals suitable for display using a television raster scanning pattern is disclosed in the U.S. Pat. No. 3,422,420 of R. J. Clark. In the Clark system the received digitally coded input character signals to be displayed in a row are stored in ordered positions in recirculating shift registers. Various timing signals, synchronized with the display scan, are generated in repetitive sequences and effectively divide the display scan into a plurality of "character space areas" of predetermined equal size. A character pattern or outline trace is formed in a character space area on the display device by blanking and unblanking the scanning beam as the beam traverses the display device. Thus, each character is formed on the display as a series of "slices" or "strokes" during successive scanlines. The character signals are read out of the recirculating shift registers one at a time, and a "character generator" subsystem generates the appropriate video stroke signals (blanking and unblanking commands) which are distinctive of the character being read out. The timing signals control the shifting and reading out of the character signals in the recirculating registers such that a new character signal is read out each time the display scan passes into a new character space area. After being read out, each character signal is restored in the recirculating registers to be recalled during the next display scanline when the next strokes of each character in the display row are generated. The retentivity of vision of the eye is relied upon to build up the impression of a complete character from the separate character strokes that are produced during each scanline.
In the U.S. Pat. No. 3,740,743 of S. N. Baron there is disclosed a television-compatible titling apparatus which generates proportionally spaced characters for display; i.e., characters which have different sized "character spaces". For example, a "W" has allotted a substantially larger character space than an "I". In the apparatus of that patent the recirculating storage is shifted in response to spacer timing signals generated by a spacer detector which is responsive to the character signals and includes means for generating spacer timing signals which are a function of the width of the character to be instantaneously displayed. A stroke generator which is responsive to the timing signals and the spacer timing signals generates a stroke of a character being instantaneously displayed.
The technique of the described Baron patent yields more pleasing titling displays, but a problem still exists in achieving character titling which is completely aesthetically pleasing; viz., the lack of the ability to display adjacent characters with "overlapping" portions. For example, consider momentarily the characters illustrated in FIG. 4. It is seen that each character occupies a given "character space". Although the spaces needn't be of constant size, as taught by the Baron patent, it is seen that there is no overlap of characters for compact presentation. In FIG. 3, the same letters are shown with overlapping portions. From the standpoint of producing characters using a television-compatible titling system which generates "strokes" or "slices" of each character during successive scanlines, it has generally been considered a complex problem to generate the type of titling shown in FIG. 3. This is because the overlapping adjacent characters "encroach" upon each other's character spaces. Thus, for each overlap situation the strokes of the successive characters need to be modified to achieve the desired patterns. This would seemingly necessitate significant additional complexity of the titling system and/or require a substantial increase in stroke memory size.
It is an object of the present invention to provide an apparatus wherein predetermined adjacent characters are presented in overlapping positions on a display, this being achieved without undue complexity or the addition of substantial memory requirements.